Synthesis of chalcogenated polyacenes

ABSTRACT

Chalcogenated polyacenes including organic semiconductors such as tetrathiotetracene, tetraselenotetracene, and hexathiopentacene are produced by reaction of a polyacene with elemental sulfur, selenium, and tellurium in the presence of nitrogen-containing hot solvents, preferably alkylated amides. N, N-dimethylformamide is the preferred solvent. The disclosed method of synthesis produces substituted polyacenes of high yield and purity in considerably shorter reaction times than achievable by prior art methods.

United States Patent [191 Perez-Alberne [54] SYNTHESIS OF CHALCOGENATEDPOLYACENES [75] Inventor: Evelio A. Perez-Alherne, Rochester,

[731 Assignee: Eastman Kodak Company, Rochester, N.Y.

[22] Filed: June 1, 1971 [21] Appl. No.: 149,056

[52] US. Cl. ..260/239 R, 260/327 M, 260/327 B, 260/327 R, 252/500 [51]Int. Cl....C07d 11/00, C07d 77/00, C07d 81/00,

C07d 83/00 [58] Field of Search ..260/327 M, 327 B, 239 R [56]References Cited OTHER PUBLICATIONS Chemical Abstracts, Vol. 44, Cols.3399-3401 (1950) abstracting Marschalk et al., Bull. Soc. Chim France(1948) pp. 418428.

[ 1 Mar. 27, 1973 Primary Examiner-Henry R. Jiles AssistantExaminer-Robert T. Bond A ttorney-Robert W. Hampton, Paul R. Holmes andT. Hiatt [57] ABSTRACT Chalcogenated polyacenes including organicsemiconductors such as tetrathiotetracene, tetraselenotetracene, andhexathiopentacene are produced by reaction of a polyacene with elementalsulfur, selenium, and tellurium in the presence of nitrogen-containinghot solvents, preferably alkylated amides. N,N-dimethylformamide is thepreferred solvent. The disclosed method of synthesis produces substituted polyacenes of high yield and purity in considerably shorterreaction times than achievable by prior art methods.

12 Claims, No Drawings SYNTHESIS OF CHALCOGENATED POLYACENES Certainpolyacenes, notably tetrathiotetracene, tetraselenotetracene, andhexathiopentacene are known to have low electrical resistivity.

Tetrathiotetracene, for example, which has the formula:

Xi olo is reported by Matsunaga in J. Chem. Phys., 42, 2248 (1965) aspossessing a specific resistance of 1040 at C when in molded form.Accordingly, such compounds are useful as organic semiconductors at roomtemperature. Additionally, these compounds have utility in that theyreadily form ion-radical salts which are themselves organicsemiconductors having even lower electrical resistivity. Matsunaga U. S.Pat. No. 3,403,165 discloses such tetrathiotetracene ion-radical saltsand their semiconductive properties.

Synthesis of substituted polyacenes has been carried out in the past byreacting a polyacene with an elemental chalcogen such as sulfur,selenium, and tellurium in the presence of hot solvent such astrichlorobenzene or Dowtherm, a eutectic of biphenyl and biphenyl oxidesold by the Dow Chemical Company. For example, tetrathiotetracene isordinarily synthesized by reacting tetracene with elemental sulfur inhot trichlorobenzene. Synthesis carried out by this method producesconsiderable amounts of undesirable by products and requires a reactiontime of from to 24 hours.

Another method for producing chalcogen-substituted polyacene compoundsinvolves the reaction of a halogenated polyacene with an elementalchalcogen in the presence of trichlorobenzene. Tetrathiotetracene can beprepared according to this method by reacting elemental sulfur with5,11- dichlorotetracene in trichlorobenzene. This method requires theadditional step of halogenating the tetracene.

Still another method for producing tetrathiotetracene involves heatingsulfur monochloride and tetracene in trichlorobenzene. Sulfurmonochloride is a very powerful reagent which must be freshly distilledbefore use. In addition, the reaction is carried out in a current ofcarbon dioxide and tends to produce significant amounts of undesirableby-products.

Accordingly, the present invention is directed to overcoming thedeficiencies of the prior art by providing methods for producingchalcogen-substituted polyacenes which require relatively short reactiontimes while practically eliminating substantial amounts of undesirableby-products. Additionally, the present invention requires no priorsynthesis of halogenated reactant or use of a strong oxidizing agent.Further, the present invention produces high yields of relatively pureproducts which can ordinarily be utilized without further purification.

It has been discovered that the shortcomings of the prior art methodsfor producing chalcogen-substituted polyacenes, particularly thosehaving the general formulas:

A/\ C) 010 W and JU C 0 01010 0 wherein X and Y each represent identicalatoms selected from the group consisting of sulfur, selenium, andtellurium, can be overcome by reacting an elemental chalcogen selectedfrom the group consisting of sulfur, selenium, and tellurium with apolyacene such as tetracene or pentacene in the presence of a reactionsolvent comprising a nitrogen-containing organic solvent, preferably analkylated amide maintained at high temperatures, usually at about refluxtemperatures. Preferred alkylated amides useful in carrying out themethod of the present invention include N,N-dimethylformamide,N,N-diethylformamide, N,N- dimethylacetamide, andN,N,N',N'-tetramethylurea. N,N-dimethylformamide is the solvent mostpreferred when carrying out the method of the present invention.

Effectiveness of the novel methods of synthesis provided by the presentinvention is demonstrated by the following examples.

Example 1 Tetracene (20 g.) and flowers of sulfur (40 g.) are placed ina flask containing 500 ml. of N,N-dimethylformamide. The reactionmixture is heated to boiling, and boiling is continued for about 3%hours. Small additions of N,N-dimethylformamide are made at intervals toreplace the solvent lost by evaporation. After the reaction is completedthe insoluble dark green product is separated by filtering while stillhot and is finally washed with benzene and ligroine. After drying underambient conditions, a yield of 29.3 g. (94.8 percent) oftetrathiotetracene is obtained. Comparison of the infrared spectrum ofthis product with that of purified authentic samples oftetrathiotetracene reveals the presence of only minor impurities. Theproduct, as prepared above, is then successfully utilized withoutfurther purification to prepare ion-radical derivatives oftetrathiotetracene as described by Matsunaga in U. S. Pat. No.3,403,165.

Elemental analysis of a typical sample of tetrathiotetracene prepared bythe method of Example 1 is as follows:

Theory (percent): C, 61.4; H, 2.3; S, 36.4; Cl, .0; N,

Found (percent): C, 61.1; H, 2.5; S, 36.4;Cl, .1; N,

Example 2 Tetracene (0.7 g.) and flowers of sulfur (1.4 g.) are placedin a flask containing 30 ml. of N,N,N',N'- tetramethylurea and providedwith a reflux condenser. The mixture is heated to boiling, and refluxedfor about 3 hours. The insoluble product is then filtered and washedwith benzene and ligroine. After drying, a yield of 0.96 g. (89 percent)of tetrathiotetracene is obtained.

Example 3 A procedure identical to that of Example 2 is used with theexception that 1 g. of tetracene, 2 g. of flowers of sulfur, and 50 ml.of N,N-dimethylacetamide are used as reagents. The yield oftetrathiotetracene is 1.2 g. (78 percent).

Example 4 A reaction is carried out as described in Example 3 with theexception that N,N-diethylformamide is used as solvent, the reactiontime is 2% hours, and the product is recovered after the reaction mediumis cooled to room temperature. The yield of tetrathiotetracene is 0.93g. (60 percent).

Example 5 Pentacene (l g.) and flowers of sulfur (2 g.) are placed in aflask containing 40 ml. of N,N-dimethylformamide and provided with anair-cooled reflux condenser. The mixture is heated to boiling, under ablanket of nitrogen gas, and refluxed in the dark for about 3% hours.The insoluble product is then filtered hot and washed with benzene andligroine. After drying in air, a yield of 1.15 g. (68.5 percent) ofblue-green hexathiopentacene is obtained.

Example 6 1. In a method for preparing a compound having the' formula:

oololoo wherein X and Y each represent identical atoms selected from thegroup consisting of sulfur, selenium, and tellurium, by a reaction ofelemental chalcogen selected from the group consisting of sulfur,selenium, and tellurium and a polyacene selected from the groupconsisting of tetracene and pentacene in the presence of a hot solvent,the improvement which comprises employing an alkylated amide as saidsolvent.

2. A method for preparing a compound having the formula:

OOlOO wherein X and Y each represent identical atoms selected from thegroup consisting of sulfur, selenium, and tellurium which comprisesreacting an elemental chalcogen selected from the group consisting ofsulfur, selenium, and tellurium with a polyacene selected from the groupconsisting of tetracene and pentacene in the presence of a reactionsolvent comprising an alkylated amide maintained at about refluxtemperatures.

3. A method for preparing a compound having the formula:

OoloO wherein X represents identical atoms selected from the groupconsisting of sulfur, selenium, and tellurium which comprises reactingan elemental chalcogen selected from the group consisting of sulfur,selenium, and tellurium with tetracene in the presence of a reactionsolvent comprising an alkylated amide maintained at about refluxtemperatures.

4. A method for preparing a compound having the formula:

COlOO W wherein X represents identical atoms selected from the groupconsisting of sulfur, selenium, and tellurium which comprises reactingan elemental chalcogen selected from the group consisting of sulfur,selenium, and tellurium with tetracene in the presence of a reactionsolvent comprising an alkylated amide maintained at about refluxtemperatures, said alkylated amide selected from the group consisting ofN,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, andN,N,N',N'-tetramethylurea.

5. The method according to claim 4 wherein said alkylated amide isN,N-dimethylformamide.

6. The method according to claim 4 wherein the elemental chalcogen isselected from the group consisting of sulfur and selenium, and thealkylated amide is N,N- dimethylformamide.

7. The method according to claim 6 wherein the elemental chalcogen issulfur and the alkylated amide is N,N-dimethylformamide.

8. The method according to claim 6 wherein the elemental chalcogen isselenium and the alkylated amide is N,N-dimethylformamide.

9. A method for preparing a compound having the formula:

A T 0 0| ol 0 o wherein Y represents identical atoms selected from thegroup consisting of sulfur, selenium, and tellurium, which comprisesreacting an elemental chalcogen selected from the group consisting ofsulfur, selenium, and tellurium with pentacene in the presence of areaction solvent comprising an alkylated amide maintained at aboutreflux temperatures.

10. A method for preparing a compound having the formula:

OOIOlG

2. A method for preparing a compound having the formula:
 3. A method forpreparing a compound having the formula:
 4. A method for preparing acompound having the formula:
 5. The method according to claim 4 whereinsaid alkylated amide is N,N-dimethylformamide.
 6. The method accordingto claim 4 wherein the elemental chalcogen is selected from the groupconsisting of sulfur and selenium, and the alkylated amide isN,N-dimethylformamide.
 7. The method according to claim 6 wherein theelemental chalcogen is sulfur and the alkylated amide isN,N-dimethylformamide.
 8. The method according to claim 6 wherein theelemental chalcogen is selenium and the alkylated amide isN,N-dimethylformamide.
 9. A method for preparing a compound having theformula:
 10. A method for preparing a compound having the formula: 11.The method according to claim 10 wherein said alkylated amide isN,N-dimethylformamide.
 12. The method according to claim 10 wherein theelemental chalcogen is sulfur and the alkylated amide isN,N-dimethylformamide.